Prior art devices for grounding electrical chassis to prevent EMI radiation from leaving the chassis and RFI radiation from entering the chassis are complex to install and have limitations once installed. A particular point of concern in providing an EMI/RFI barrier to circuits within an electronic system chassis is EMI and RFI radiation leakage at receptacles that connect external cables to internal circuitry of the chassis. It is important that a ground exist at the receptacles for all EMI and RFI radiation that may be otherwise communicated through the chassis at the receptacle. One attempt to ensure that this undesirable radiation does not leak out of or into the chassis is to use an EMI/RFI gasket at the receptacle.
The prior art EMI/RFI gaskets, however, have significant limitations. First of all, prior art gaskets mimic the associated receptacle's shape. Many receptacles for electrical connectors have a "D"-shape that facilitates properly orienting the connector to the receptacle. These gaskets typically comprise small thin metal plates that fit over the receptacle to connect the receptacle to a cover plate that further connects to electrical ground. Unfortunately, gaskets that mimic this "D"-shape are difficult to install because they too must be oriented.
Another limitation of conventional EMI/RFI gaskets is that, while they fit the "D"-shaped gasket, they can not fit over all types of fastening points that permit fastening the connector to the receptacle. That is, receptacles typically include either screwholes or hexagonal posts to which fastening screws of the connectors attach. The existing EMI/RFI gaskets are designed to only fit the screwholes that are part of the receptacle. There is not an EMI/RFI gasket that accommodates both screwholes and hexagonal posts or many of the other various types of attachment or fastening points for fastening the connector to the receptacle.
A third important limitation associated with the prior art EMI/RFI gaskets has to do with their installation on the electronic system chassis. These gaskets typically fit on or over the receptacle beneath the cover plate. The gaskets are typically placed on the receptacle and are only held by means of gravity to the receptacle. Thus, upon removal of the cover plate, the gaskets may fall from the back cover of the chassis and down into or near other electronic devices or connections to the chassis or otherwise interfere with system maintenance or operation. This is an undesirable feature of the prior art EMI/RFI gaskets that, if avoided, could significantly simplify both their functioning, as well as overall maintenance of the associated electronic system.
It is an object of the present invention, therefore, to provide an improved EMI/RFI gasket that overcomes the limitations of prior art EMI/RFI gaskets. It is an object of the present invention to provide an EMI/RFI gasket that serves as a barrier to the transmission of EMI and RFI radiation to and from an electronic system chassis having an electrical receptacle for receiving an electrical connector and at least one fastening point for fastening the electrical connector to the receptacle. The chassis for which the EMI/RFI gasket has use has an electrically grounded cover plate to cover a predetermined portion of the chassis near the receptacle. The cover plate connects the chassis to an electrical ground. The EMI/RFI gasket of the present invention provides a gasket plate having a flat, flexible, electrically-conductive material with sufficient surface area to adhere and electrically connect to the cover plate, while maintaining flexibility sufficient to move upon the cover plate and gasket being placed over the receptacle. This promotes electrical contact among the receptacle, connector and the gasket plate. The receiving slot exists in the gasket plate for receiving the receptacle and permitting the use of a wide variety of fasteners associated with the connector. The receiving slot is symmetrical about a longitudinal axis and a latitudinal axis of the gasket plate. A plurality of deflected teeth are formed from the gasket plate and positioned around a predetermined portion of the receiving slot. The deflected teeth are deflected from the gasket plate to contact the connector at points separated by not greater than the predetermined distance that maintains an electrical ground connection between the cover plate and the connector. The predetermined distance is determined partially by estimated wavelengths of the EMI radiation and the RFI radiation.
It is also an object of the present invention to provide an EMI/RFI gasket that is easier to install for a wider variety of applications than prior art EMI/RFI gaskets.
It is a further object of the present invention to provide an improved EMI/RFI gasket that, once installed, permits removal of the chassis cover plate without the gaskets falling from their associated receptacles.